Post-processing Lightsabers in Blender
Here is what I came up with:

Adding a glow without affecting close parts of the handle:


The handle mesh is on scene layer 6
The  blade and other objects are on scene layer 1





Create a material for the blade:


Enable Transparent in Render settings > Film:


Create two renderlayers, one for the handle and one for the blade:

 

By setting the handle layer to be masked by the blade, we get the glow to be added behind the nearer parts of the handle.
Enable the Object index pass for the blade renderlayer, and set the Pass index of the blade to 1 in Properties > Object > Relations.
Composite nodes: (click for full size)




Result:



Reflections and refractions:

Technique one:

Without and with reflections and refractions blurred: (click for full size)

 

Limitations:


Reflections of reflections of the blade will not have glow applied. (likewise for refractions)
The glow on reflections and refractions will be applied on top of reflections/refractions of the handle.


Here is a Blendfile for you to inspect.

Technique two:


All objects except for the handle and the blade are visible on layer one
Refractive or reflective objects are visible on layer 7 as well as layer 1
Objects that are not refractive or reflective are visible on layer 3 as well as layer 1
The blade is on layer 2
The handle is on layer 6





Enable Transparent in Render settings > Film:


Create four renderlayers: (click for full size)

 

 
Composite nodes: (click for full size)




Here is a blend for technique two

Advantages:


Applies glow to inter reflections/refractions


Limitations:


Materials that are both reflective/refractive and something else (e.g. diffuse) will be blurred. The only way to really solve this with compositing is to put each partially diffuse/reflective object on its own renderlayer.



You could fix this particular example by adding separate materials for the glossy/diffuse aspects of the shader and separating with the Material index pass.
The glow on reflections and refractions will be applied on top of reflections/refractions of the handle.



You could fix this by adding another renderlayer, but this will use up more render time and it may not be worth it for such a small detail.